On September 22, the Anza team announced the initiation of the Alpenglow activation process within the public Solana testnet. This new consensus mechanism aims to reduce the target block finalization time from approximately 12.8 seconds to just 150 milliseconds.
Alpenglow is coming to testnet this week. š§µ
ā Anza (@anza_xyz) September 22, 2026
Testnet exercises the exact migration devnet and mainnet-beta will run.
The Alpenglow community cluster rehearsed the migration numerous times and has been running Alpenglow for over 4 months.
Now Alpenglow moves to the formalā¦
As of this writing, the official tracker from Anza lists SIMD-0326 under Pending Testnet Activation.
Source: GitHub.Alpenglow will entirely replace the existing Solana consensus mechanism, which is based on TowerBFT and Proof-of-History. The first phase of the upgrade, known as Votor, is included in Agave 4.3. Another component, Rotor, which is intended to succeed Turbine in the data distribution mechanism, will be introduced in a separate SIMD.
Currently, validators cast votes via transactions, with finalization requiring a confirmation accumulation over 32 slots. In Votor, participants will send votes directly to each other and combine them into certificates using BLS signatures.
Under optimal conditions, Votor allows for block finalization in a single voting round. If the necessary support isn't achieved right away, the protocol will utilize an additional round along with various types of certificates.
The targeted 150 milliseconds pertains specifically to finalization time, not the duration of the slot. The latter will be reduced in Solana through separate updates. For everyday users, the transaction submission mechanism will remain unchanged: Alpenglow does not affect SVM, transaction formats, fees, or account models.
For infrastructure services, however, the changes are more significant. Agave 4.3 introduces the bank_id field in Geyser and gRPC streams, allowing for differentiation among multiple candidate banks within a single slot. Indexers, explorers, and trading infrastructures are advised to buffer events by the pair (slot, bank_id).
After the transition to Alpenglow, the practical distinction between the statuses of confirmed and finalized will nearly vanish. Both will initially remain in the API, but confirmed is expected to be removed later. Vote transactions will no longer appear in blocks, and Proof-of-History will cease to dictate their production rate.
Transition Process
Before the public testnet activation, Alpenglow had been operational for over four months in a dedicated community cluster, where developers rehearsed the migration multiple times. The same procedure will now be sequentially carried out for the testnet, developer network, and the mainnet beta of Solana.
The transition is outlined in a separate SIMD-0384. The migration boundary is set to occur after 5000 slots following the activation of the feature gate. Until that point, the network will continue operating on TowerBFT.
Once this boundary is reached, new blocks will temporarily exclude user transactions, allowing only votes to be included.
Validators will wait for a block to receive an enhanced optimistic confirmation from 82% of the stake. The last ancestor of this block before the migration boundary will become the genesis block of Alpenglow. After collecting the BLS certificate, validators will roll back later blocks, switch the consensus to Votor, and once again permit user transactions.
This mechanism is necessary to avoid rolling back already confirmed user operations during the consensus transition.
On September 21, Anza recommended Agave 4.3 for general use by beta mainnet validators. The same timeline indicates September 28 as a preliminary date for resuming activation of release features.
At the time of writing, SOL is trading near $120, having increased by 1.2% in the last 24 hours and 21.2% over the week.
Hourly chart of SOL/USDT on Binance. Source: TradingView.To recall, in September 2025, the Solana community approved SIMD-0326, with 98.94% of participants voting in favor of implementing Alpenglow.
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